In recent years, as acoustic devices which are worn on heads of users for use such as earphones or headphones (which may hereinafter be referred to as “head mounted acoustic devices”), in addition to devices that simply output acoustic information, devices with functions in which use situations are considered have become widespread. As a specific example, a head mounted acoustic device capable of suppressing ambient sounds (so-called noise) coming from an external environment and enhancing a sound insulation effect using a so-called noise canceling technique is known. Patent Literature 1 discloses an example of an acoustic device using such a noise canceling technique.